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991.
Determination of gamma emitting radionuclides in shallow marine sediments off the Sindh coast has been carried out using a gamma spectrometry technique. The activity concentration measured in various sediment samples off the Sindh coast has been found to vary from 15.93 +/- 5.22 to 30.53 +/- 4.70 Bq kg(-1) for 226Ra, from 11.72 +/- 1.22 to 33.94 +/- 1.86 Bq kg(-1) for 228Ra and from 295.22 +/- 32.83 to 748.47 +/- 28.75 Bq kg(-1) for 40K. The calculated mean values of radium equivalent activity, absorbed dose rate and effective dose are 98 Bq kg(-1), 49 nGy h(-1) and 0.06 mSv y(-1), respectively. No artificial radionuclide was detected in the samples measured from the study area. As no data on radioactivity of the coastal environment of Pakistan are available, the data presented here will serve as baseline information on radionuclide concentration in shallow sea sediments off the Sindh coast. The data will also be useful for tracking pollution inventories from unusual radiological events (if any) in the territorial waters of the study area. Further, the information presented will contribute to modelling of a regional radioactivity database from the perspectives of the International Atomic Energy Agency's Asia-Pacific Marine Radioactivity Database and Global Marine Radioactivity Database. 相似文献
992.
The effect of an external electric field on laser-generated plasma has been studied. It is observed that the laser-generated plasma can be used for the ignition of a spark in the presence of a low voltage external electric field. An eight-fold emission intensity enhancement in Cu Ⅰ spectral lines are measured as compared to the signal intensity in the absence of an external electric field.The plasma parameters remain the same initially, up to a few microseconds after the generation of plasma, and this feature makes it more interesting for the quantitative analysis of any sample using laser induced breakdown spectroscopy(LIBS). In the presence of an external electric field,fluctuations(contraction and expansion) in the laser-generated plasma are observed which increase the plasma decay time and consequently result in enhanced signal intensity. 相似文献
993.
Abou Bakr M. Salama Ahmad Gebreil Tamer M. A. Mohamed Riham R. E. Abouleisa 《International journal of molecular sciences》2021,22(14)
Unlike some lower vertebrates which can completely regenerate their heart, the human heart is a terminally differentiated organ. Cardiomyocytes lost during cardiac injury and heart failure cannot be replaced due to their limited proliferative capacity. Therefore, cardiac injury generally leads to progressive failure. Here, we summarize the latest progress in research on methods to induce cardiomyocyte cell cycle entry and heart repair through the alteration of cardiomyocyte plasticity, which is emerging as an effective strategy to compensate for the loss of functional cardiomyocytes and improve the impaired heart functions. 相似文献
994.
Deep-level transient spectroscopy (DLTS) measurements were carried out on low-doped n-silicon before and after irradiation with 5.48 MeV α particles at room temperature with a fluence of 1010 α particles/cm2. The DLTS measurements on the samples identified three electron levels E1, E2 and E3 before irradiation. The deep-levels characteristic studies include emission rate signatures, activation energies, defect concentrations and capture cross sections. It was found that all pre-existing defects decreased their amplitudes during irradiation. The decrease in activation energy of level E3 and noticeable suppression of level E1 was also observed after irradiation. It was clearly seen that the composite peak E3 (combination of E2 and E3) was successfully resolved after irradiating with α particles. α-irradiation is seen to lead a significant suppression of the iron interstitial defect, and without causing any change in its room temperature annealing characteristics. 相似文献
995.
Amir Hassannia Ahmad Darabi Mustafa Alshamali 《IEEJ Transactions on Electrical and Electronic Engineering》2009,4(5):668-673
Dynamic modeling of synchronous generators is of great importance in power system studies. Three-phase sudden short circuit test is the basic conventional method applied for determining the parameters of synchronous generators. The conventional curve fitting yields to non-unique and inaccurate solutions depending on the initial guesses and nature of the numerical methods. In this paper, a genetic algorithm based method is developed for curve fitting process and identifying uniquely the dynamic parameters through a new fitness function. Owing to the problems associated with sudden short circuit test and unavailability of experimental results, the test is performed on an exact model of the generator with harmonics content space dependent inductances gathered from finite elements analysis. The parameters of a 31.5 kVA alternator are evaluated by use of the proposed method and compared with measured parameters available for this machine by manufacturer showing a good approximation. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
996.
Ghulam Murtaza Abdul Ghafoor Manzoor Qadir 《Journal of the science of food and agriculture》2008,88(1):100-107
BACKGROUND: In most parts of Pakistan, untreated city effluent is utilised for growing vegetables around large urban settlements such as Faisalabad. Farmers use it as a source of irrigation water and plant nutrients. However, its continuous use may have serious environmental implications, since it also contains heavy metals. In this study the Faisalabad city effluent was examined for irrigation quality and its impact on irrigated soils and vegetables. RESULTS: Irrigation hazard of the effluent was moderate (electrical conductivity (EC) 1.1–1.7 dS m?1, Sodium adsorption ratio (SAR) 5.9–17.4 mmol1/2 L?1/2, Residual sodium carbonate (RSC) 1.0–2.1 mmolc L?1) at site 1 and strong (EC 3.7–4.1 dS m?1, SAR 16.1–21.8 mmol1/2 L?1/2, RSC 4.0–9.1 mmolc L?1) at site 2. Mean concentrations of ammonium bicarbonate/diethylene triamine pentaacetic acid (AB/DTPA)‐extractable Cd, Co and Mn at upper soil depth (0.0–0.2 m) were respectively 0.080, 0.057 and 217.4 mg kg?1 at site 1 and 0.101, 0.076 and 164.1 mg kg?1 at site 2. CONCLUSION: The concentrations of Cd and Mn were above the permissible limits but that of Co was below the permissible limit for irrigation. The concentrations of Cd, Co and Mn tended to decrease with increasing soil depth. Accumulation of metals was higher in leaves irrespective of whether leaves were the edible or non‐edible component of shoots. Use of untreated city effluent for irrigation without risk assessment and management could be a serious hazard, impacting soil and crop quality and ultimately human health. Copyright © 2007 Society of Chemical Industry 相似文献
997.
Multi-phase ac motor drives are nowadays considered for various applications, due to numerous advantages that they offer when compared to their three-phase counterparts. In principle, control methods for multi-phase machines are the same as for three-phase machines. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information of the rotor speed is extracted from measured stator currents and voltages at motor terminals. Vector controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open-loop estimators and closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an open-loop and model reference adaptive system (MRAS)-based sensorless control of vector controlled five-phase induction machine with current control in the stationary reference frame. The MRAS-based sensorless operation of a three-phase induction machine is well established and the same principle is extended in this paper for an IRFOC five-phase induction machine. Performance, obtainable with hysteresis current control, is illustrated for a number of operating conditions on the basis of simulation results. Full decoupling of rotor flux control and torque control is realised. Dynamics, achievable with a five-phase vector controlled induction machine, are shown to be essentially identical to those obtainable with a three-phase induction machine. Experimental verification is also provided. 相似文献
998.
Noushin Mohammadifard Carolyn Gotay Karin H. Humphries Andrew Ignaszewski Ahmad Esmaillzadeh 《Critical reviews in food science and nutrition》2019,59(15):2375-2385
ABSTRACTAppropriate intake of micronutrient, such as electrolyte minerals is critical for the well-being of the cardiovascular health system. However, there are some debates regarding the impacts of dietary and/or supplemental intake of these minerals, on the risk of cardiovascular events and associated risk factors. High sodium intake is adversely associated with the risk of hypertension. Although many reports refered to the positive association of Na intake and cardiovascular events and all-cause mortality, however, other studies indicated that low Na intake is related to higher risk of all-cause mortality and HF-related events. By contrast, dietary potassium, magnesium and calcium have an inverse correlation with cardiovascular events and risk factors, especially with blood pressure. There are some controversies about cardiovascular effects and all-cause mortality of high Ca intake, including no effect, preventive or adverse effect with or without vitamin D. Calcium supplementation might be beneficial for prevention of cardiovascular events and all-cause mortality only in individuals with low intake. Moreover, calcium intake showed a J- or U-shaped association with the risk of cardiovascular diseases. Due to the controversies of the effect of electrolyte minerals especially sodium and calcium intake on cardiovascular events, large scale, well-designed long-term randomized clinical trials are required to evaluate the effect of minerals intake on cardiovascular events and all-cause mortality. In this review, we discuss the role of dietary and or supplemental sodium, potassium, magnesium, calcium, in cardiovascular health, as well as their clinical applications, benefits, and risks for the primary prevention of cardiovascular disease, in general population. 相似文献
999.
Nomana Kalsoom Muhammad Zafar Mushtaq Ahmad Shazia Sultana Anwer Usma Asma Jabeen 《Microscopy research and technique》2019,82(7):1012-1020
In present study, the schizocarp morphology of 14 species belonging to Apiaceae family has been investigated. Light microscopy (LM) and scanning electron microscopy (SEM) have been utilized to highlight qualitative and quantitative features of studied species. Variations have been observed in macro‐ and micro‐morphological features such as color, shape, symmetry, length, width, apex, epicuticular projections, surface patterns, anticlinal, and periclinal wall patterns. Schizocarp shapes observed were oval, round, triangular, linear, elliptic, and globose. Fruit was either homomorphic or heteromorphic. Crystalloids, stellate hair, multicellular spines, and platelets were mostly observed epicuticular projections. Surface patterns on the fruit surface were striate, rugulate‐striate, reticulate, and striato‐knotted. Both macro‐ and micro‐morphological characters can serve as an important tool in classifying Apiaceae family at various taxonomic ranks. Substantial variations observed can assist as useful constraints at various taxonomic levels as they provide reliable and constant details. Disparities observed in schizocarp features can pave a path for Apiaceae family classification based on phylogenetic and molecular studies. 相似文献
1000.
Saba Gul Mushtaq Ahmad Muhammad Zafar Saraj Bahadur Shazia Sultana Najla Begum Syed Nasar Shah Wajid Zaman Fazal Ullah Asma Ayaz Uzma Hanif 《Microscopy research and technique》2019,82(7):1021-1031
The present study is insight into pollen morphology for characterizing species and their utility in the taxonomic separation of certain taxa of subfamily Nepetoideae (Lamiaceae) from Pakistan. The pollen micromorphology of 11 species of the Nepetoideae was analyzed and documented using light microscopy and scanning electron microscopy (SEM) for both qualitative and quantitative characteristics. Most species have hexazonocolpate pollen grains but trizonocolpate and tetrazonocolpate pollen with circular and oval amb were also rarely observed in Mentha spicata. The basic pollen shape in most of the studied species was subspheroidal but prolate grains were also observed in M. spicata, S. coccinea, and S. plebeia. The exine sculpturing of Nepetoideae pollen was taxonomically very informative particularly at subfamily level. Observations of exine sculpturing with SEM revealed various types of pollen grains: reticulate, bireticulate, microreticulate, perforate, aerolate, and gammate. The bireticulate type further subdivided into three subtypes based on the number of secondary lumina in each primary lumen and is characterized by varying characteristics of the secondary reticulum and primary muri. A significant variation was observed in colpus surface ornamentation. The maximum polar diameter was found in O. americanum (58 ± 5.8 μm) and the maximum equatorial diameter observed in O. basilicum (50.25 ± 1.37 μm). Pollen features of the studied species were discussed and compared based on the current taxonomical concepts. The results showed that pollen traits of the subfamily Nepetoideae was found significant to classify the taxa. Furthermore, pollen features provide additional evidence to distinguish macromorphologically similar taxa from each other. 相似文献